The present invention relates to a seatbelt apparatus installed in a vehicle for restraining and protecting an occupant with a seatbelt. More particularly, the present invention relates to a tongue which is slidably supported to a seatbelt and can be latched with a buckle fixed to a vehicle body or the like and to a seatbelt apparatus employing the tongue.
Vehicle seats have been equipped with seatbelt apparatuses. In the event of an emergency, such as a vehicle collision where a large deceleration acts on the vehicle, such a seatbelt apparatus restrains an occupant with a seatbelt so as to prevent the occupant from falling out of the seat, thereby protecting the occupant.
Among the conventional seatbelt apparatuses, a three-point type seatbelt apparatus is generally known. A well known three-point type seatbelt apparatus has a webbing composing a seatbelt for restraining an occupant. The webbing has one end fixed to the vehicle body and a second end wound into a seatbelt retractor, which is fixed to a lower portion of the vehicle body. A belt guide (deflection fitting) guides the webbing which is fixed to an upper portion of the vehicle body, such as a center pillar, in such a manner as to allow the pullout of the webbing from the seatbelt retractor. Between the one end fixed to the vehicle body and the belt guide, a tongue is supported to the webbing to freely slide along the webbing. The tongue can be latched with a buckle fixed to the vehicle body or the like, thereby restraining an occupant sitting in a vehicle seat. In this case, a portion of the webbing between the belt guide and the tongue functions as a shoulder belt for restraining the shoulder and the chest of the occupant, while a portion of the webbing between the one end fixed to the vehicle body and the tongue functions as a lap belt for restraining the lap (lumbar) of the occupant.
In the event of an emergency such as a vehicle collision where an extremely large deceleration acts on the vehicle, an emergency locking mechanism of the seatbelt retractor is activated to stop the pullout of the webbing so as to prevent the forward movement of the occupant due to inertia, thereby restraining and protecting the occupant. In recent years, the seatbelt retractor or the buckle is provided with a pretensioner. In the event of an emergency, the pretensioner activates to pull the webbing to rapidly remove slack of the webbing so as to minimize the forward movement of the occupant.
Generally, the webbing is inserted into a belt through hole formed in the tongue. Therefore, the webbing is bent at the tongue so that the shoulder belt obliquely extending from the shoulder of the occupant to a lower portion and the lap belt extending in the lateral direction along the lumber of the occupant are defined relative to the tongue.
However, since the shoulder belt and the lap belt are defined only by bending the webbing at the tongue, the lap belt slightly increases in length due to inertial force of the occupant so as to allow the forward movement of the occupant in the event of emergency.
A tongue has been proposed in which a locking bar is rotatably supported to a frame having a latch plate which can be latched with the buckle (for example, see Japanese Patent Publication No. H07-71522, which is hereby incorporated by reference herein in its entirety). In this case, the locking bar is rotated because of a pulling force applied to the webbing, whereby the webbing is clamped between the locking bar and the frame.
The tongue disclosed in Japanese Patent Publication No. H07-71522 clamps the webbing between the locking bar and the frame in the event of emergency, thereby blocking the lap belt from increasing in length.
A tongue has been proposed in which a tongue plate is provided with a locking member in such a manner as to allow pivotal movement of the locking member and the locking member is continuously biased by a torsion spring. The tongue has a space between the tongue plate and the locking member to allow the free relative movement of the webbing and the tongue plate in the ordinary use (for example, see Japanese Patent No. 3544322, which is hereby incorporated by reference herein in its entirety).
According to the tongue disclosed in Japanese Patent No. 3544322, since the space for allowing the movement of the webbing between the locking member and the tongue plate is ensured by the torsion spring, the tongue plate smoothly moves relative to the webbing when the occupant puts on or take off the seatbelt, thereby providing improved usability of the tongue.